The present invention relates to the modification of polysaccharides.
Polysaccharides, such as starch, cellulose, pectin, hemicellulose and the like have a diversity of applications. Starch for instance has long formed part of the diet of humans and many animals. In addition to food applications, different non-food applications have been developed for starch and also for many other polysaccharides. The industrial use of starch in particular has increased enormously in recent years. Cellulose in turn is for instance used in the production of paper, in textiles, building materials etc.
The polysaccharides occurring in nature have specific properties which are sometimes less suitable for particular applications. In order to provide a polysaccharide with the desired properties for a particular application use is often made of chemical modification. Chemical modification has the drawback that it involves one or more additional processing steps. In addition, the chemical processing of products used in foods has a somewhat undesirable ring to the consumer nowadays.
It is the object of the invention to provide an alternative, natural manner of modifying polysaccharides. In addition, the invention has for its object to provide new polysaccharides for new application possibilities.
This is achieved by the invention with a method comprising of placing the polysaccharide in contact with a sugar group-transferring enzyme and a sugar group donor. In this manner an enzymatic modification takes place, wherein no (undesirable) chemical agents are used.
According to the invention a distinction can be made between direct and indirect modification. Direct modification entails the sugar group, which is transferred from the sugar group donor, being (covalently) linked to the polysaccharide to be modified. Indirect modification means there is no direct linking but that changes are made in the physiological appearance of the polysaccharide by the sugar group-transferring enzyme. As example hereof can be mentioned the inclusion in a starch granule of a second polysaccharide formed by the sugar group-transferring enzyme. In addition, the transfer of a sugar group to a water molecule can also be seen as an indirect modification. In such a transfer to water, sucrose is cleaved into glucose and fructose. Due to such a cleaving the physiological conditions in the plant cell change which can result in a change in the physiological appearance of the polysaccharide, such as for instance in the form and size of a starch granule.
The sugar group-transferring enzyme can be any enzyme which, as the name already indicates, transfers a sugar group from a sugar group donor to an acceptor molecule. Such enzymes are usually referred to as transferases. The acceptor molecule will usually be the polysaccharide to be modified. In the case of indirect modification there is another acceptor, such as sucrose of glucose. In the case of transfer to water, water is the acceptor and the enzyme is usually referred to as invertase. In principle, all transferases have to a greater or lesser extent the capacity to use water as acceptor. These enzymes are called transferases or invertases in accordance with the proportion of transferase or invertase activity. The sugar group for transferring can consist of one or more sugar units. In the case of invertases or invertase activity only one sugar unit is transferred.
The invention relates particularly to the use of fructosyl transferases or glucosyl transferases as sugar group-transferring enzymes and fructosyl donors and glucosyl donors as sugar group donor. In the continuation of the application fructosyl transferases and/or glucosyl transferases in particular will be discussed by way of example. Other sugar group-transferring enzymes can however be applied instead of these without departing from the invention. The transfer of a sugar group to water is also included hereinbelow.